1. Field of the Invention
The present invention relates in general to electrochemical cells/batteries, and more particularly, to an electrochemical cell that comprises stackable lithium ion batteries which may have any three dimensional freeform geometric configuration and which require only a lightweight casing.
2. Background Art
Lithium ion rechargeable batteries for use in all types of applications are well known in the art. Generally, lithium batteries are desirable over other types of rechargeable batteries, including nickel cadmium and nickel metal hydride batteries, due to their lighter weight, energy density and overall efficiency, among other advantages.
Generally, it is desirable to have as light of a battery as possible. Indeed current lithium ion batteries have been produced which have the capacity and the cyclability for use in all types of consumer devices, including, but not limited to portable telephones and lap top computers. However, the current batteries utilize relatively heavy and cumbersome casings.
In particular, battery casings generally comprise a rigid and heavy material in a generally cylindrical or prismatic shape. The rigid material prevents buckling of the casing which is caused by internal pressures. The internal pressures are derived from the generation of gas through the decomposition of the electrolyte or of various constituents within the battery. In addition, the casings are typically nickel plated steel which reduces the likelihood of corrosion.
Further, especially in prismatically shaped cells, the individual cells that comprise a battery are generally strongly biased against each other through the use of spring plates. The use of strong spring plates increases the weight of the battery. In addition, the spring plates occupy space which could otherwise be used for additional cells which could then increase the capacity of the battery.
Lastly, these batteries, due to the necessary housings and spring plates to apply uniform pressure onto the cells, are generally available in common, simple configurations, such as cylinders, prisms, cubes and other box-like shapes and configurations. As such, where the battery container is of a shape that is not such a common shape, the prior art utilizes conventionally shaped batteries within the non-uniform battery container. As a result, a portion of the space within the battery container remains empty, and, in turn, comprises dead space.